The shooting happened near Hubbard Street and Clark Street in River North at around 4 a.m.
The 38-year-old security guard works for Boss Bar and came back to the River North area when he heard looters were there, sources told ABC7.
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The victim got into a "physical altercation with a group of unknown offenders on the sidewalk," police said.
Mike McCafrey, who lives near the scene, described the victim as "jovial."
"Always looking out for everybody, I guess he caught one last night- unbelievable," he said.
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The 38-year-old is in critical condition at Northwestern Memorial Hospital as of Monday afternoon.
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Investigators were seen picking up shell casings in the area late Monday morning.
Area Three detectives are investigating the shooting.
During the chaos and gunfire, a bullet flew through the glass of Lyfe Kitchen
"There is a bullet hole through the front door, through the vestibule. Thank god no one was inside," said Gail Taggert at Lyfe Kitchen. "We just reopened a month ago and now we have to shut down again."
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